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  • AIP Publishing  (5)
  • Ding, Ning  (5)
  • Huang, Jun  (5)
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  • AIP Publishing  (5)
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  • 1
    Online-Ressource
    Online-Ressource
    AIP Publishing ; 2010
    In:  Physics of Plasmas Vol. 17, No. 6 ( 2010-06-01)
    In: Physics of Plasmas, AIP Publishing, Vol. 17, No. 6 ( 2010-06-01)
    Kurzfassung: This paper is to numerically investigate, in one dimension, the effects of precursor plasma resulted from wire-array ablation on the performance of its following implosion after the ablation. The wire-array ablation is described by an analytic model, which consists of a rocket model or Sasorov’s expression of wire-array mass ablation rate, the evolution equation of magnetic field, and several roughly reasonable assumptions. The following implosion is governed by the radiation magnetohydrodynamics. The implosion processes of wire-array Z-pinch from plasma shells prefilled and un-prefilled by the low-density plasma inside them are studied, and that from the wire-array ablations, which may be changed through varying the ablation time, ablation rate, and ablation velocity Vabl, are also simulated. The obtained results reveal that the prefilled low-density plasma and the precursor plasma from the wire-array ablation help to enhance the plasma shell pinch and the final implosion of the wire array, respectively, compared to the pinch of un-prefilled plasma shell. With the same plasma masses, which are distributed in the interior of the array and the shell, and modified Spitzer resistivity, the implosions that start from the wire ablation develop faster than that from the plasma shell with the prefill. If more substance ablates from the wire array before the start of its implosion, the final Z-pinch performance could be better. The Z-pinch plasma is highly magnetized with driven current more than 3 MA.
    Materialart: Online-Ressource
    ISSN: 1070-664X , 1089-7674
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2010
    ZDB Id: 1472746-8
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Online-Ressource
    Online-Ressource
    AIP Publishing ; 2014
    In:  Physics of Plasmas Vol. 21, No. 7 ( 2014-07-01)
    In: Physics of Plasmas, AIP Publishing, Vol. 21, No. 7 ( 2014-07-01)
    Kurzfassung: Implosion dynamics of nested wire arrays in (r, θ) geometry was studied with two-dimensional magnetohydrodynamic (2D MHD) simulations. Three different implosion modes are obtained by just changing the wire number of the outer array, when the other conditions, such as the initial radius, length, mass of each array, the wire number of the inner array, and the discharge voltage waveform, are fixed. Simulation results show that the effect of discrete wires, which cannot be described by the thin shell inductive model, will influence the distribution of current between the outer and inner arrays at the early stage, and the discrepancy between results from MHD and thin shell model increases with the interwire gap of the outer array.
    Materialart: Online-Ressource
    ISSN: 1070-664X , 1089-7674
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2014
    ZDB Id: 1472746-8
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Online-Ressource
    Online-Ressource
    AIP Publishing ; 2012
    In:  Physics of Plasmas Vol. 19, No. 6 ( 2012-06-01)
    In: Physics of Plasmas, AIP Publishing, Vol. 19, No. 6 ( 2012-06-01)
    Kurzfassung: The implosion dynamics of wire-array Z-pinches are investigated numerically in 2D (r, θ) geometry by using a resistive MHD code. It is assumed that the wires have expanded to plasmas with diameter d0, which is used as the initial condition for the consequent implosion process. In fact, the explosion process of individual wires is not included. By changing d0, the effects of the wire expansion degree on the implosion dynamics are analyzed. When d0 is larger, the current density is more concentrated at the outer side of the wires and the fraction of current flow around the wire plasmas is nearly in proportion to d0. As a result, the ablation rate of wires is increased and the implosion phase starts earlier. This conclusion agrees with the simulation works of other authors [Chittenden et al., Phys. Plasmas 11(3), 1118 (2004)]. When the array radius and initial wire plasma diameter are fixed, the increase of wire number leads to the azimuthal merge of wires during implosion. When the wires number exceed a critical value, which is related to d0, wire plasmas can merge to a continuous shell with an azimuthal perturbation in density, which depends on the initial wires number.
    Materialart: Online-Ressource
    ISSN: 1070-664X , 1089-7674
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2012
    ZDB Id: 1472746-8
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    In: Physics of Plasmas, AIP Publishing, Vol. 19, No. 12 ( 2012-12-01)
    Kurzfassung: Implosions of (quasi-)spherical loads with mass redistribution and displacement modification are investigated numerically. Both methods can theoretically counterbalance the nonuniformity of magnetic pressure along the load surface and realize quasi-spherical Z-pinch implosions. Mass redistribution is feasible for spherical loads with large radius and weight, while the displacement modification is more suitable for light loads, such as those composed of wire arrays. Simulation results suggest that, for mass redistributed spherical loads, wall instabilities induced by polar mass flows will deform the imploding shell. For prolate spherical loads, in which the wall instability cannot develop, the kinetic energy distribution is disturbed at high latitude. These passive behaviors and their possible mitigation methods, such as reshaping the electrode, are investigated numerically in this paper.
    Materialart: Online-Ressource
    ISSN: 1070-664X , 1089-7674
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2012
    ZDB Id: 1472746-8
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Online-Ressource
    Online-Ressource
    AIP Publishing ; 2011
    In:  Physics of Plasmas Vol. 18, No. 4 ( 2011-04-01)
    In: Physics of Plasmas, AIP Publishing, Vol. 18, No. 4 ( 2011-04-01)
    Kurzfassung: The dynamics of ablated plasmas of wire-array Z-pinches are studied numerically in (r,θ) geometry by using the magnetohydrodynamic (MHD) simulation model in which the mass injection boundary conditions are presented, and two-dimensional spatio-temporal distributions of magnetic field and precursor current during the ablation phase are obtained. The ablated-plasma dynamics contains four processes: drifting toward the axis, arriving at the axis and forming the precursor column, and contraction and expansion of the precursor column. The relationship among the maximum inward velocity of ablated plasma streams and the initial wire array parameters is analyzed and it is found that this velocity is relatively sensitive to the change of inter-wire separation but weakly depends on the original array radius. The results are in reasonable agreement with the experiments on MAGPIE facility. The origin of the current flow in the precursor plasmas is analyzed from the point of view of the B-field convection in (r,θ) plane. The dynamics of ablation streams determine the distribution of magnetic field and the current density Jz inside the wire array. The precursor current can be approximately calculated by the integral of Jz inside the region of a radius near to the column. In this model, the fraction of precursor current is less than 10% of the total current, which is close to the experimental results. When the current waveform is fixed, the increase of the inter-wire gap or decrease of the initial radius will lead to the increase of the precursor current.
    Materialart: Online-Ressource
    ISSN: 1070-664X , 1089-7674
    Sprache: Englisch
    Verlag: AIP Publishing
    Publikationsdatum: 2011
    ZDB Id: 1472746-8
    Standort Signatur Einschränkungen Verfügbarkeit
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